1. Field of the Invention
The present invention relates to an ophthalmic apparatus which obtains characteristics of an eye to be examined and a method for storing ophthalmic information therefor.
2. Description of Related Art
It is known for apparatuses which obtain characteristics of the eye to be examined, such as a corneal shape analyzing apparatus, a sectional view analyzing apparatus for analyzing a degree of opacities of a cornea or a crystalline lens and a shape of each part of an anterior part of the eye based on an image of a sectional view thereof.
For example, it is known for the corneal shape analyzing apparatus which projects a placido ring target onto a cornea, then photographing an image of the target by using a photographing camera, thereby calculating a curvature distribution over a wide range of the cornea, based on the obtained image data of the eye. The curvature distribution is visualized as the topography.
On calculating a corneal curvature, firstly, a plurality of standard balls having a known curvature are photographed whereby the image data are obtained. A calibration data is obtained based on the image data and the curvature of respective balls. Thereby, based on both of the calibration data and the image data of the eye, an analyzed result converted to an absolute value is calculated. The calibration data is intrinsic for the apparatus, therefore it is not shared by the same model apparatus due to the intrinsic difference. In the case of above mentioned corneal shape analyzing apparatus, the following are listed as the intrinsic difference: dispersion, displacement or the like of a placido ring, its mounting position and a photographing camera provided for a photographing optical system. The calibration data is used for the purpose that the analyzed result may not involve the intrinsic difference. The calibration data is usually stored in a memory of the apparatus in the form of a calibration data file.
Certainly, although the calibration data is intrinsic for the apparatus, if the obtained and analyzed result is stored, and the topography is re-displayed on another apparatus, then there is no difference between contents of displays.
In contrast, an apparatus which has a re-analysis function is known. The function is such as to store a raw image data of an eye which is obtained by using the photographing camera, then calling the raw image data and obtaining an analyzed result based on a calibration data.
However, referring to such apparatus that use calibration data as described above, there are problems as follows.
Firstly, such apparatus that stores only an analyzed result converted to an absolute value can not utilized for a new analyzing method. For example, in the case of examining variation of the analyzed result by way of obtaining results at a fixed period of time extending over a long period of time in order to carry out a historical observation, even if an operator makes an effort to interrupt the analysis and to adopt a new analyzing method, the operator can not use the new analyzing method with respect to such data as obtained in the past.
There is such possibility that an apparatus which has a function for storing a raw image data may adopt a new analyzing method by way of calling the raw image data, provided the identical apparatus is used. If the raw image data, obtained by using another apparatus, is analyzed by mistake, then reliability of the analyzed result is deteriorated due to the different calibration data. In addition, even if the identical apparatus is used, once the calibration data is changed by way of re-calibrating the apparatus, the re-analyzed result of the raw image data, obtained before or after calibration, can not achieve high accuracy.